Periodic inspection of process equipment such as reactors, heat exchangers, distillation towers, storage tanks, and pipelines is typically performed to measure the effects of corrosion or erosion using non-destructive test methods. The inspection process is more difficult for insulated equipment and typically requires numerous inspection ports cut through the insulation material and any metal jacket at locations most susceptible to corrosion and erosion. Depending on the equipment and the insulation material, inspection ports range from open holes in the insulation material and metal jackets to access plates that are fastened over a hole in the metal jacket to contain a removable section of insulation.
U.S. Pat. No. 5,014,866 describes an inspection port which includes an elastomeric, flanged tube and a metal, flanged cap for sealing a hole in a metal jacket containing a layer of insulation around process equipment. The elastomeric tube has a cylindrical body that has a relaxed outside diameter larger than the hole in the metal jacket in order to grip the jacket. The metal cap fits tightly within the elastomeric tube and assists in sealing the tube within the hole in the metal jacket. The tube has a length sufficient to contact the edges of holes through flat or corrugated metals. Both the tube and the cap are flanged to prevent over insertion and the flange of the cap is sized to protect the flange of the tube. Inspections are conducted by removing the cap and any exposed insulation. However, the tube frequently falls out after the cap is removed, especially when installed in corrugated metal jackets.